Python - loop back to raw_input if user gives an invalid response?

Question

I have some Python code using raw_input(). I want to automatically go back to the raw_input if the user gives an invalid response. How do I do this?

first code:

name = raw_input("Enter Name: ")

If the user presses Enter without giving a name (which can be anything) how would I go back to raw_input?

second code:

def start():
        answer = raw_input("Go outside (y,n)? ").lower()
        if answer == "y":
                print "I agree! We've only been here for a few days. Let's do some more exploring!"
        elif answer == "yes":
                print "I agree! We've only been here for a few days. Let's do some more exploring!"
        elif answer == "no":
                print ""
                raw_input("I think we should do some more exploring; we've only been on this planet for a few days... (Press 'Enter')")
        elif answer == "n":
                raw_input("I think we should do some more exploring; we've only been on this planet for a few days... (Press 'Enter')")
                print ""
        else:
                print "Press 'y' for yes and 'n' for no"

start()

I'm trying to go back to raw_input if 'else' occurs or if the user responds with "n" or "no"...

Thanks! What does the "True" part of "while True:" mean, though? Does it just act like a on and off switch or something? — James, Oct 02 '15 at 21:47
while True is potentially an infinite loop, you use logic inside the while to decide when it should end, like in your case keep going until the user enters one of the valid choices — Padraic Cunningham, Oct 02 '15 at 21:50

ShadowRanger · Answer 1 · 2015-10-02T21:47:52.543

1

Try a while loop?

name = ''
while not name:
    name = raw_input("Go outside (y,n)? ").rstrip().lower()

edited Oct 02 '15 at 21:47

answered Oct 02 '15 at 21:09

ShadowRanger

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I don't really understand that; could you go into a bit more depth, please? – James Oct 02 '15 at 21:12
@James To do something more than once you need a loop. `while` is one of the types of loops (`for` is another). So you call raw_input(), check to see if the user entered anything. While they haven't, do it again. – dsh Oct 02 '15 at 21:15
This is actually wrong, the OP should loop until name is in a set of valid strings, this will break the loop without getting some valid input – Padraic Cunningham Oct 02 '15 at 21:17
@PadraicCunningham: The original question asked for empty or not, I agree valid or not would be more correct. Also, @dsh, the `.lower()` you removed was part of the original code, I kept it to have similar behavior (the cost of lowering being almost nil if the string is empty, and needs to be paid regardless if it is not. – ShadowRanger Oct 02 '15 at 21:47
Yep, by name not evaluating to False would not mean that the user entered suitable input, just that they did not enter nothing. – Padraic Cunningham Oct 02 '15 at 21:51

Python - loop back to raw_input if user gives an invalid response?

first code:

second code:

1 Answers1